Seafloor spreading is the process by which new oceanic lithosphere is created at divergent plate boundaries, where oceanic ridges form and rift valleys develop. Subduction zones occur when one oceanic plate is forced under another plate, often forming deep trenches on the seafloor and continental volcanic arcs or volcanic island arcs above the subducting plate.

1. Chapter 9 Section 3 Shaeed Marshall Per. 1

2. Key Concept 1. What Is Seafloor Spreading? -Seafloor Spreading is the process by which plate tectonics produces new oceanic lithosphere.

3. Key Concept 2. What Is A Subduction Zone? -A Subduction Zone occurs when one oceanic plate is forced down into the mantle beneath a second plate.

4. Oceanic Ridge A continuous elevated zone on the floor of all major oceans basins and varying at the crests of ridges represent divergent plate boundaries

5. Rift Valley A Rift Valley is a deep faulted structure found along the axes of divergent plate boundaries; Rift valleys can develop on the seafloor or on land.

6. Trench A Trench is a surface feature in the seafloor produced by the descending plate during subduction.

7. Continental Volcanic Arc Continental Volcanic Arcs are mountains formed in part by volcanic activity caused by the subduction of oceanic lithosphere beneath a continent.

8. Volcanic Island Arc A Volcanic Island Arc is a chain of volcanic islands generally located a few hundred kilometers from a trench where subduction of one oceanic slab beneath another is occurring.

9. The End. The End